Mitel Sx 200 El/ml Technicians Handbook

Troubleshooting and Repair
61
Troubleshooting
4. To return the circuits to service, select: 
DIAGNOSTICS
MORE_KEYS
RET-TO-SVC .
Replacing a Main Controller Card
When replacing a main controller card (MCC), you must ensure that the 
replacement MCC and the installed MCC match – both in card type 
and stratum clock type. This procedure applies to the MCC II,
MCC IIIEL, MCC Yields, MCC IIIML, and the MCC in the SX-200 
LIGHT/DIGITAL PBX.
1. Quit the customer data entry mode. 
2. If you do not have an...

Technician’s Handbook
62
Correcting Ground Path Problems
Safety ground absorbs the dangerous voltages that come in contact 
with the PBX cabinet. The safety ground connects to the PBX through 
the ground termination of the system’s three-prong power cord.
System ground provides a stable ground reference for the voltages the 
the system uses. The system ground attaches to the PBX through a 
separate ground wire (6 AWG recommended) that connects directly to 
a system cabinet ground-stud. 
In most...

Troubleshooting and Repair
63
Troubleshooting
Ground Path AC Voltage Test
This test measures the presence of AC voltage in the metallic loop.
1. With your meter connected in the same way as you did for the resis-
tance test, measure the AC voltage.
2. Start with your meter set for high AC voltages and adjust it down 
until you get a reading.
3. You should get a reading of 1 Vac or less.
If your reading is greater than 1 Vac, check to see if your electrical panel 
ground connects to the building ground....

Technician’s Handbook
64
6. The resistance between the two grounds should be less than five 
OHMS. If not, try alternate ground point(s) and repeat the test.
Testing the CO and PBX Ground Differential
If a PBX experiences trunk lock-ups, or trunk seize failures, perform the 
CO/PBX Ground Differential Test.
This test determines whether the DC ground potential between the 
selected building ground point and the CO ground point is within 
acceptable limits by measuring the two currents: “Loop” current and...

Troubleshooting and Repair
65
Troubleshooting
4. Measure the Ring current:

Set the meter to Milliamperes = DC and Range = 200 
Milliamperes.

Connect the meter between the Ring trunk lead and the 
building’s open-ended ground wire. Be sure that you disconnect 
the building ground wire from the PBX ground-stud.
5. Allow sufficient time for the current to stabilize and record the Ring 
current.

DC Ring current = ________________________
6. Calculate the CO/PBX ground potential by dividing the Ring...

Technician’s Handbook
66
BCC III (DSP Module)
Sixteen DTMF receivers are provided by a DSP module on a BCC III.
DTMF Receivers (DSP on MCC IIIEL, MCC IIIELx, MCC IIIML, or 
MCC II)
Seven DTMF receivers are standard on each MCC
(CDE Form 04,Option 68).
CLASS / DTMF Receivers (SPINE Control Module II)
Seven DTMF receivers are standard on Control Module II. Receivers 
not assigned as CLASS receivers are available to the system as DTMF 
receivers. CLASS receivers are only available to the devices in the...

Troubleshooting and Repair
67
Troubleshooting
Checking the FIM/CIM Carrier Cards
1. Verify that the cards with the interface module are installed in the 
correct card slot for the assigned bay.
2. Verify that the interface modules in the main control cabinet are 
correctly connected to its peripheral bays.The configuration 
positions are hard coded in the software.
3. Verify that the same distance variant of FIM is installed at each end 
of the link.
4. Verify that the dip switch on the Control Triple...

Technician’s Handbook
68
Checking the T1 Card, T1/E1 Module, 
and the PRI Card

In the SX-200 EL system, LIGHTWARE 17 supports one digital bay 
with two T1 trunk cards and the other digital bays with one T1 trunk 
card to total a maximum of seven T1 trunk cards.
LIGHTWARE 18 and greater supports a maximum number of eight 
T1 links in the SX-200 EL system. These links can be from the T1 
cards and from the T1/E1 modules. Any bay can have a maximum 
of two T1 links to a total of eight T1 links in the...

Troubleshooting and Repair
69
Troubleshooting
Checking the Number of T1 
Trunk Cards
With LIGHTWARE 18 Release 2.0 or greater software, any peripheral 
bay can have up to two T1 cards to a total maximum of eight T1 links 
(with T1 Cards and T1/E1 modules) in the system. 
Prior to LIGHTWARE 18 Release 2.0, the maximum number of T1 
cards was seven. The following table defines the maximum number 
(prior to LIGHTWARE 18) of T1 Trunk cards in peripheral bays that can 
connect to a Control Triple FIM Carrier...

Technician’s Handbook
70
Trunk Signaling and Supervision
General Signaling & Supervision Concepts
All trunks share similar basic handshaking functions. The actual 
signaling mechanism will vary with the trunk type. 
Seize: (request to make a call) The calling party initiates the call by 
requesting service from the called party.
Seize Acknowledgment: (ready to receive) The called party indicates 
that the call can commence. 
This acknowledgment occurs when the calling party expects a 
response (Dial...